Put the flour, cocoa powder and baking soda in a bowl together, stir to combine.

Put the butter in the bowl of a stand mixer with the paddle attachment fitted, mix until smooth. Add the salt and the sugar and mix until light and fluffy.

Add the cocoa mixture in two batches and beat until it begins to come together into a dough.

Tip the dough onto a work surface and knead it into a ball until it comes together.

Wrap this into a block and cover in clingfilm, leaving it to set in the fridge for at least 1 hour until firm.

Preheat the oven to 140C Fan/160C, and line two baking trays with parchment. Take the dough from the fridge and roll it out between two sheets of greaseproof paper until it is about 1/2cm in thickness. Using a 6cm cutter, stamp out rounds of dough and place them on the prepared baking tray evenly spaced apart, they wont spread too much.

You may need to gather up the dough and form it back into a ball and roll it out again to make 32 rounds. If the dough has got too warm, you can roll it out and place it back in the fridge to firm up before cutting it out.

Bake for 15-17 mins until small cracks appear on the surface, leave the biscuits to cool on the tray for 10 mins (they will be quite soft), before moving to a rack to cool completely.

To make the filling, sift the icing sugar into a bowl and add 50ml of the double cream, beat the mixture until it forms a thick paste that won't leak out of the cookies. Add more cream if necessary, add the peppermint extract to taste.

Take the cookies and pair them up, sandwiching them together with the filling, place in the fridge to firm up, they can be stored in the fridge for about a week.